CMI Annual Report 2021

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conditions that favor tropical cyclone genesis (“genesis probability” in the left panel of Figure 13.1) or the frequency of pre-TC “seeds” (center panel). However, the combined effect of variations in genesis probability and seeds yields a sharp annual cycle that accurately explains hurricane climatology across both climate models and observations (right panel). The ability of this theoretical framework to explain the annual cycle of hurricanes provides an observational test of the hypothesis, developed in climate simulations, that the combined role of seeds and genesis probability in the climate impacts hurricane frequency. Figure 13.1. TC seeds and genesis probability together explain the annual cycle of North Atlantic (NA) hurricane frequency in observations and climate models. Scatter plots of monthly climatology of NA TC frequency versus TC genesis probability index (left panel), frequency of vortex seeds (center panel), and the combination of both (right panel) from observations and model historical simulations from HiRAM, AM2.5, and AM2.5C360. All the quantities are normalized by their annual total. Dashed lines show the linear regression, for which the equation and the variance explained are shown on the bottom right of each panel. The sharp annual cycle of Atlantic hurricane frequency is due to the combined effect of both seeds and genesis probability (Yang et al., 2021). A related study explores the impact of TC seeds on genesis across a broad suite of climates and climate model configurations and develops a theory to link seed frequency to large-scale environmental factors (Hsieh et al., 2022, submitted). This work has shown that inter-model spread in TC genesis sensitivity to changing climate is largely driven by differences in the response of pre-TC synoptic disturbances. The climatological changes in these disturbances can be understood in terms of changes to large-scale aspects of the atmosphere (such as the amount of energy converging in the atmosphere and the rate at which air ascends). The researchers are now working to connect observed and modeled changes in TC frequency to large-scale climatic parameters using first principles (e.g., conservation of energy, mass and momentum), in an effort to build a theoretical constraint on tropical cyclone frequency. The Vecchi team also explored impacts of uncertainties in ocean temperature reconstructions and changes in hurricane monitoring as a way to assess past changes in hurricane activity. They found that improvements in ocean temperature 53 Carbon Mitigation Initiative Twenty-first Year Report 2021
estimates over the 20 th century allow for a reproduction of multi-decadal historical tropical cyclone frequency changes with high-resolution atmospheric models. This has enhanced confidence in the models’ ability to reproduce future changes in TC frequency (Chan et al. 2021). The researchers have also extended a methodology to account for the impact of past changes in hurricane monitoring on tropical cyclone frequency estimates. This has allowed the researchers to build a homogenized record of major (Category 3-5, the most destructive storms) hurricanes in the Atlantic from 1851-2020. This new homogenized record suggests that expected centuryscale increases in major hurricane frequency have been masked by a combination of multi-decadal climate variability and late-20 th century aerosol forcing. The Vecchi team is currently developing high-resolution climate model simulations to test this hypothesis. In addition to developing a new understanding of the climatetropical cyclone connection, the team have worked to review the state of the literature and highlight key open challenges. This work has appeared in two review articles, one on tropical cyclones and global warming (Knutson et al., 2021) and the other on tropical cyclone frequency more generally (Sobel et al., 2021). Relevance to bp bp has long been interested in tropical cyclone risk because of the vulnerability of its coastal and offshore infrastructure, and because increases in the severity or frequency of tropical cyclones is an important driver of public opinion in support of the energy transition. The most interesting conclusion of the highlighted studies is that the 20 th century increase in the frequency of major hurricanes would now be higher if not for past and ongoing anthropogenic aerosol emissions (primarily from coal combustion), which will continue to decrease during the energy transition. In the near term, we should thus expect more rapid increases in the frequency of major hurricanes than would be expected because of elevated greenhouse gases alone. Carbon Mitigation Initiative Twenty-first Year Report 2021 54
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Annual Report 2021
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Contents INTRODUCTION 1 RESEARCH -
Page 5 and 6: The Carbon Mitigation Initiative (C
Page 7 and 8: Annual Meeting For the second conse
Page 9 and 10: Erin Mayfield (left), a postdoctora
Page 11 and 12: Research - At a Glance Toward Accel
Page 13 and 14: Modeling Large-Scale CO 2 Injection
Page 15 and 16: Diverging Fate of Oceanic Oxygen Mi
Page 17 and 18: Louisiana is an attractive initial
Page 19 and 20: Office of the Governor of Louisiana
Page 21 and 22: Bridging the Gap Between CCS Ambiti
Page 23 and 24: Figure 2.2. Comparison of historica
Page 25 and 26: REPEAT Project Provides Real-time L
Page 27 and 28: and the public. The REPEAT Project
Page 29 and 30: Figure 4.1. Magnitude of different
Page 31 and 32: Soil Uptake and Methane Feedback of
Page 33 and 34: industrial level because most of cu
Page 35 and 36: more methanogenic (Figure 6.1a, Wil
Page 37 and 38: Modeling Large-Scale CO 2 Injection
Page 39 and 40: The most sensitive parameter in the
Page 41 and 42: Improving Forecasts of How Biodiver
Page 43 and 44: The Efficiency of Enhanced Weatheri
Page 45 and 46: Figure 9.2a-b. Map of ACCE (a) and
Page 47 and 48: full sunlight but die quickly in sh
Page 49 and 50: Future Fires Compromise Amazon Fore
Page 51 and 52: Figure 11.1. Emergence of alternati
Page 53 and 54: For the first time, the researchers
Page 55: Understanding Tropical Cyclone Freq
Page 59 and 60: Calcium (Ca)-Based Solid Sorbents f
Page 61 and 62: This Year’s Publications Allen, M
Page 63 and 64: Larson, E., C. Greig, J. Jenkins, E
Page 65 and 66: Wang, C., B.J. Soden, W. Yang, and
Page 67 and 68: The cover and text pages of this re
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